WASHINGTON -- The Supreme Court's decision 50 years ago, although an immense blessing to the nation, also carries a melancholy lesson. It is that great events -- the school desegregation ruling was the largest judicial event since the Dred Scott case of 1857 -- have myriad reverberations, some beneficial, others not.

Brown v. Board of Education accelerated the process of bringing this creedal nation into closer conformity to its creed. But the decision also encouraged the abandonment of constitutional reasoning -- of constitutional law. It invested the judiciary with a prestige that begot arrogance. And it seemed to legitimize a legislative mentality among judges wielding an anti-constitutional premise. The premise is that ``unjust'' and ``unconstitutional'' are synonyms.

The board of education being sued for its segregation policies was not in the South, but in Kansas -- Topeka. Segregation was widely practiced, and even more widely approved. Yes, in Montgomery, Ala., it was illegal for a white to play checkers in public with a black. But Congress was running a segregated school system in the nation's capital. In 1948, President Truman could not persuade Congress to make lynching a federal crime.

When the case was first argued in 1952, the Supreme Court was composed entirely of Democratic -- of Roosevelt and Truman -- nominees. And if the court's composition had not been soon and unexpectedly changed by the addition of a Republican nominee, the legal basis of segregation -- the doctrine that ``separate but equal'' public facilities are constitutional -- probably would have been affirmed.

No Republican nominee had served on the court since Owen Roberts, a Hoover nominee, resigned in 1945. But in 1953, eight months in to Dwight Eisenhower's presidency, there occurred the most fateful heart attack in American history. It killed Chief Justice Fred Vinson, a Kentuckian who believed the ``separate but equal'' doctrine, enunciated in an 1896 decision, should remain.

Four other justices were, to varying degrees, inclined to agree. Cass Sunstein of the University of Chicago Law School, writing in The New Yorker, notes that the waspish Justice Felix Frankfurter said that Vinson's heart attack was ``the first indication that I have had that there is a God.'' But Frankfurter and another liberal-leaning justice, Robert Jackson, were FDR appointees who had learned the virtues of judicial modesty by watching the judicial hubris of the court as it struck down many of FDR's early New Deal measures.

Vinson's death preceded a rehearing of the case. His replacement, Earl Warren, governor of California, was a post-New Deal politician. He was comfortable with the premise that the federal government's responsibilities extend to the general amelioration of citizens' conditions. A man of immense charm in the court's face-to-face politics, he also was impatient with the idea that justices must go only where led by judicial reasoning about the Constitution's text as it has been illuminated by precedents based thereon.

Some Northern states had segregated schools when they ratified the 14th Amendment. It includes the guarantee of ``equal protection of the laws'' that the court in 1954 decided was incompatible with segregated schools. To reach this conclusion, the court cited social-science evidence that segregation induced feelings inimical to young children's self-esteem, thereby injuring their capacity to learn.

That this rationale was window dressing became clear when the court invoked the Brown decision to outlaw segregated beaches, golf courses, etc. The court would have done better with this simple argument:

The ``separate but equal'' doctrine came from a correct understanding that equality for blacks was the intent of the 14th Amendment. But the court in 1896 erred because, when separation is enforced on racial lines, ``separate but equal'' is inherently oxymoronic.

When the Brown ruling was rendered, Thurgood Marshall, the NAACP's lead litigator, expected segregation to be gone in five years. But 10 years later, only 1.17 percent of Southern black schoolchildren attended public schools with whites.

In 1954, the court's majesty could not compel compliance. Today the court's reserves of prestige are immeasurably greater, partly because of what it did then. What also is much enlarged is the public's belief that judicial fiats can and should remedy many social ills, broadly defined to include the refusal of legislatures to adopt polices deemed just.

``John Marshall has made his decision: now let him enforce it.'' That supposedly was President Andrew Jackson's response to a Supreme Court decision he disliked. Then, as now, the court's power flowed largely from its prestige, which was not sufficient to bend Old Hickory. No president could act similarly today. This progress owes much to what happened May 17, 1954.